Cutter particularly for gear hobbing

ABSTRACT

The present invention relates to a cutter for gear cutting work, particularly a cutter capable of gear cutting work of high precision, and having throw-away type insert cutter tips which can be replaced easily.

United States Patent 1 Shioya [111 3,740,808 [451 June 26, 1973.

I CUTTER, PARTICULARLY FOR GEAR nonnmc [75] Inventor: Kazuma Shioya,Yao-shi, Osaka-fu,

Japan [73] Assignee: Dijet Industrial Company Limited,

Osaka, Japan [22] Filed: Dec.-16, 1971 [21] Appl. No.: 208,823

[30] Foreign Application Priority Data Dec. 16, 1970 Japan 45/113348Dec. 16, 1970 Japan 45/126976 [52] U.S. CI 29/105 R, 29/103 B [51] Int.Cl. B261! l/l2 [58] Field of Search 29/105 R, 103 B [56] ReferencesCited UNITED STATES PATENTS 3,571,875 3/1971 Grandi 29/105 R 3,303,5542/1967 Bateman ct a]. 29/103 B 2,693,020 11/1954 Pelphrey 29/105 RPrimary Exqminer l eonidas Vlachos Attorney-Roberts B. Larson, WilliamR. I-Iinds et'al.

[5 7] ABSTRACT The present invention relates to a cutter for gearcutting work, particularly a cutter capable of gear cutting work of highprecision, and having throwaway type insert cutter tips which can bereplaced easily.

4 Claims, 14 Drawing Figures 1 CUTTER, PARTICULARLY FOR GEAR HOBBINGBACKGROUND OF THE INVENTION Hobs for gear cutting work are generally ofcomplicated form, having numerous cutting edges on their periphery.

"Conventional hobs having numerous cutting edges formed directly ontheperiphery of the hob body are being used widely. However, these hobs areuneconomical since it is necessary to replace the entire hob when itscutting edges are damaged or worn out.

Further, being mostly constructed from high-speed steel, these solidhobs are poor in durability and remarkable in abraison after use.Consequently, the drilled flutes of hob cutting edges must be groundfrequently, and the grinding thereof requires skill and a great deal oftime as well since it must be done very accurately. Moreover, these hobsmade from high-speed steel are limited in their cutting speed in gearcutting work, necessitating the adoption of an extensive feed in orderto increase efficiency. Consequently, the gear shape of the works to becut departs substantially from the genuine involute curve, with theresult of crudely finished surfaces. Therefore, in order to make up forsuch defects as above, it is necessary to do finishing work by geargrinding and shaving, with accurate regrinding additionally required,all of which are very much troublesome.

On the other hand, a built-up hob is being used as an improved type overthe conventional hobs, in which the hob body is equipped with cutterblades formed separately therefrom, aiming at an economical effectthrough possible replacement of said cutter blades alone. However, asthese blades are in the form of a body incorporating numerous cuttingedges formed in a lateral series, the blades themselves become prettylarge in size and very complicated in shape, making it very difficult toregrind them when they are worn out, as in the case of a hob ofintegrated type.

Furthermore, it is impossible in fact to continue to use these built-uphobs only by replacing their cutter blades because their principalbodies will also be found fairly damaged when the cutter blades becomeuseless after repeated re-grinding thereof.

It has been attempted to increase gear cutting efficiency by means ofsintering of the hob material, but because of the difficulty ofre-grinding, not to mention the difficulty of relieving grinding forprecise tooth form due to the difficulty of grinding cemented carbides,hobs made of cemented barbides have hitherto been not in general useexcept for micron hobs.

It is, therefore, an object of the present invention to eliminatecompletely the aforesaid defects of the conventional hobs and provide acutter which can be used in a very economical way through replacement ofits insert tips alone, whichare formed separately from and fitted to thehob body.

Another object of this invention is to provide such insert tips ofsuitable form for cemented carbides and capableof being used repeatedlyby reversing them inside-out and topside down, increasing thereby thenumber of times of their use as well as their utility, worthy of thecost of expensive materials such as cemented carbides.

A further object of thisinvention is to provide a cutter capable ofcarrying out the forming, fitting and replacement of its insert tipsvery easily and quickly.

A still further object of this invention is to provide a cutter in whichthe cutter body has on its periphery a plurality of tip locatorspositioned at fixed intervals'in a peripheral direction so as to befixed simultaneously by means of a pair of tightening devices allowingeach locator to support a number of tips with ease and accuracy, therebymaking it possible to do gear cutting work of high precision withoutcausing any crookedness in the tooth forms to be cut.

Yet another object of this invention is to provide a cutter in which,with the tops positioned in parallel in an axial direction, a pluralityof tips can be tightened simultaneously and securely by means of a wedgeand a clamping bolt, causing the tip fixing parts not to get loose andthe tip supporting parts to be damaged as little as possible.

The objects as abovementioned can be attained by the improvement of thepresent invention, and embodiments thereofwill be made clearer by thefollowing detailed disclosure in conjunction with the drawings attachedhereto.

According to the present invention, the cutter is so constructed thatthe peripheral surface of its cutter body has a number of insert tips sofixed thereon as to be detachable for easy replacement by means of aplurality of locators, wedges and clamping bolts, said insert tips beingof throw-away type and capable of being reversed for use in differentorientations, and also capable of being fixed securely in correctpositions respectively.

BRIEF DESCRIPTION OF THE DRAWINGS Hereunder is given a brief descriptionof the drawings showing a typical embodiment as well as an improvedembodiment of the present invention:

FIG. 1 is a side view of a typical hob body assembly according to thepresent invention, partly in section and exploded;

FIG. 2 is a front view of the hob body assembly taken substantially onthe line 2 2 of FIG. 1;

FIG. 3 is an enlarged front elevation of the insert tip of throw-awaytype;

FIG. 4 is an enlarged side elevation of the insert tip of throw-awaytype taken substantially on the line 4 4 of FIG. 3;

FIG. 5 is an enlarged upper plan of the throw-away type insert tip takensubstantially on the line 5 5 of FIG. 3;

FIG. 6 is an enlarged front elevation of the locator partly broken away;

FIG. 7 is a plan of the locator taken substantially on the line 7 7 ofFIG. 6;

FIG. 8 is a front elevation showing an improved embodiment of hob bodyassembly according to this invention;

FIG. 9 is a sectional view taken substantially on the line 9 9 of FIG.8;

FIG. 10 is an enlarged front elevation partly broken away of an improvedtype locator to be used for the improved type hob body assembly shown inFIG. 8;

FIG. 11 is a plan of the locator taken substantially on the line 11 llof FIG. 10;

FIG. 12 is a front elevation showing a typical embodiment of theimproved type throw-away insert tip according to the present invention;

FIG. 13 is a plan taken on the line 13 13 of FIG. 12; and

FIG. 14 is a front view with the principal part partly broken andomitted, of the hob body assembly equipped with the improved type inserttip illustrated in FIG. 12.

DESCRIPTION OF THE PREFERRED i EMBODIMENTS Now, referring to FIG. 1 andFIG. 2 illustrating a typical embodiment of the present invention, thecutter body has spiral flutes 21 on its periphery and a plurality ofplain flutes 22 positioned at fixed peripheral intervals and parallelwith the body axis, a plurality of tip supporting parts 23 being formedin the manner of hob teeth between said spiral flutes 21 behind eachplain flute 22, and grooved wedge fitting holes 24 and tapped holes 25also being formed ahead of each plain flute 22.

Similar to ordinary hob teeth, each of said tip supporting parts 23 isarranged as a spiral having the lead angle (a) on the pitch circle ofthe teeth with respect to each plain flute 22, and also is so formed asto produce a negative rake angle ,8 of the tip seats 26 formed in frontof them, the size thereof being smaller than the insert tips 27.

Each of the insert tips 27 is fixed to the cutter body 20 so as to bedetachable by means of a plurality of locators 29, a plurality of wedges31 and clamping screws 32, said locators 29 having plural tip supportingholes 28 and said wedges 31 having slopes for tightening the tips; eachlocator 29 being so fitted in the plain flutes 22 as to place each tipsupporting hole 28 in the correct position opposite to the root of toothof each tip supporting part 23 of the cutter body 20; each insert tip 27leaned on the tip seat 26 with its lower part engaged with the tipsupporting hole 28 being clamped by means of clamping bolts 32 with thewedge 31 engaged with the wedge fitting hole 24. Thus, it is intended toobtain an economic effect through repeated use of the cutter body 20which is made possible by mere replacement of the insert tips 27 alone.

Further, these insert tips 27 are supported in an inclined state on eachtip seat 26 which has a negative rake angle B with an adequate tipclearance given thereto. Said rake angle B is more or less variable inproportion to the diameter of the cutter body 20, the thickness of theinsert tip 27 and the cutting work conditions but is preferably formedat about 6 in general.

Furthermore, as shown in FIG. 1, in said clamping bolts 32, bothleft-handed screws and right-handed screws are used, for example,left-handed screw 34 matching to the left-handed tapped hole 33 providedin the wedge 31 and right-handed screw 35 matching to the right-handedtapped hole 25 provided in the cutter body 20. However, differentialscrews may also be employed therein.

Next, describing the insert tip 27 in detail: the upper part of each tip27 is formed as the tip body 36 and the lower part as its setting side37 (FIG. 1). For a basic form thereof, it is contemplated to form thetip body 36 in the shape of a flat block having a profile of theoreticaltooth form corresponding to said rake angle {3 6 and to form the settingside 37 into any form as desired.

Now, as these insert tips are usually made from materials of highanti-abrasive quality such as cemented carbides, ceramics and thermit,it is desired to increase their utility worthy of the cost of thematerials as much as possible.

Thereupon, these tips take a form of throw-away type as shown in FIGS. 35.

Referring to FIGS. 3 5, the lower part of each tip formed as settingside 37 is now turned into a sub-tip 38 by forming it like the tip body36 formed at the upper part of the tip, each sub-tip 38 taking a posturereversed by 180 upside down with respect to the upright tip body 36, andthus a throw-away tip being formed by incorporating the tip body 36 andsub-tip 38 into a body at the root of tooth thereof.

In other words, the tip body 36 has two parallel flat faces 39 40, twosides 41 42 and a top plane 43, said flat faces 39 40 having a profileof theoretical tooth form corresponding to said rake angle [3 --6. Thesubtip 38 has also flat faces 44 45, two sides 46 47 and a top plane 48.

Further, said flat faces 39 and 44 as well as 40 and 45, respectively,form two parallel polygonal faces, the top plane 43 of the tip body 36and the top plane 48 of the sub-tip 38 being formed parallel with eachother and vertical to said flat faces 39 40 and 44 45.

Furthermore, said insert tip 27 is fitted in parallel to the hob axis,and both sides 41 42 of the tip body 36 are made oblique to the flatfaces 39 40 by said lead angle a, while both sides 46 47 of the sub-tip38 are made oblique in a reversed state and in the opposite direction tosaid sides 41 42 by a negative lead angle a.

Thus, it will be seen clearly that at each edge line of both the insideand outside of the tip 27, cutting edges are formed in the tip body 36such as 49 50 51 at the outside and 52 53 54 at the inside, andsimilarly cutting edges 55 56 57 and 58 59 60 respectively in each sideof the sub-tip 38.

When cutting work is done by tip body 36, sub-tip 38 serves as a settingside, while when cutting is done by sub-tip 38 by reversing it, tip body36 acts as a setting side. Thus, both the tip body 36 and sub-tip 38 arecapable of having a combined function of cutting and setting. Now it canbe understood that it is possible to obtain thereby effective throw-awaytype tips each of which can be used four times in total by reversingitself inside out and upside down.

In the embodiment of the invention illustrated in FIGS. 3 5, both of thetip body 36 and sub-tip 38 are formed into a body so as to have thededendum line in common. However, both of them may be incorporated witheach other via a central flat portion of an adequate length (not shown).

Next, the locator 29 shown in FIG. 6 and FIG. 7 is for positioning eachplurality of tips 27 correctly in the axial direction and is formed inthickness approximately equal with said tips 27, and it has apluralityof tip supporting holes 28 provided in its upper side portion at thesame pitch as the axial pitch of the tip supporting parts 23 of saidcutter body 20.

. Each of these tip supporting holes 28 is formed so as to correspond tothe shape of the lower portion of the tip 27.

Consequently, when the lower portion of the tip 27 is formed as asetting side 37 of a different shape from that of the upper portion ofthe tip body 36, each tip 27'is to be positioned so as to be reversibleinside out by forming said tip supporting holes 28 to correspond to saidsetting side 37 in their shapes engaging the latter 37 with the former28. However, when said setting side 37 is formed as a sub-tip 38 likethe tip body 36 (see FIGS. 3-5), each tip supporting hole 28 is to beformed to correspond to these sub-tips 38 and the tip body 36 in itsshape.

Thereby, it becomes possible to support the tip 27 to be reversibleupside down and inside out by alternative engagement of each tipsupporting hole 28 and said sub-tip 38 with each other. Both sides 28L28R are to be inclined at a lead angle a respectively like sides 46 47of the sub-tip 38 in upright position.

Further, each locator 29 is arranged circumferentially at fixedintervals through engagement with a plain flute 22 of the cutter body20, and the tip supporting holes 28 of each circumferentially adjacentlocator are arranged along a spiral direction with a lag of[ l/number ofplain flute 22] X [pitch of tip supporting part 23], these being formedto be capable of taking a correct position at the root of tooth of eachtip supporting part 23.

Now, as shown in FIG. 1 and FIG. 2, each locator 29 is fitted to eachplain flute 22 so as to make each tip supporting hole 28 correspondcorrectly to each tip supporting part 23, and each tip 27, the lowerportion of which engages with respective tip supporting hole 28, is sofixed as to be detachable freely by means of wedge 31 and clamping screw32 so that the tip 27 can be fixed securely in a bit projected positionfrom the tip supporting part 23.

In the typical embodiment of the fixing method for said locators 29shown in FIG. 1 and FIG. 2, each of these locators 29 is fixed with useof a binding agent so as to have it engaged with each plain flute 22 ofthe cutter body 20, but these locators 29 can be fixed mechanically bymeans of a pair of clamping rings 61 62 and a plurality of clampingbolts 63 as shown in FIGS. 8, 9 and 14.

The improved type locator 64 shown in FIGS. 9 11 has tapers 65 66 formedat both ends of its upper side portion, and a plurality of said locators64 are fixed at a time by pressing the tapers 67 68 formed inside theperipheral portion of the clamping rings 61 62 against said tapers 6566.

In this case, circular concave portions 69 70 are formed at both ends ofthe cutter body into which the clamping rings 61 62 are insertedrespectively, clamping being done in this state by means of a pluralityof clamping bolts 63.

The wedges 31 for tightening said tips 27 engage with the wedge fittingholes 24 provided on the cutter body 20, and the tips'are tightened bymeans of clamping screws 32 in such a state that the tips are pressedagainst the tip seats 26 of the cutter body 20 by the tip clampingslopes 30 formed in the backsides thereof. In the embodiment illustratedin FIG. 1 and FIG. 2, each tip 27 is fixed respectively by means of awedge 31, but it is possible, when desired, to fix two tips 27 at a timeby forming the wedge 31 to have'a large width as shown in FIG 8.

The improved type wedge 71 illustrated in FIG. 8 is formed to have awidth twofold of the tooth width. With use of the improved wedge 71, itbecomes possible to fix two tips 27 in a correct position at a time byhaving the rear inside 72 of the wedge fitting hole 24 of the cutterbody 20 and the backside 73 corresponding thereto of the wedge 71respectively formed in curved surfaces and through self-alignment of theguide of said arcs 72 73. V

Thereby, in cutting work of small-pitched teeth with use of smallpitches, said simultaneous fixing of two tips 27 by a single wedge 71makes it possible to increase working efficiency through a reducednumber of items' to be used and simplified fitting thereof, and at "thesame time, it becomes possible to do cutting work of high precisionthrough accurate function of the wedge 71 on each tip 27 which will notbe caused to be crooked in its position preventing works from being cutin crooked tooth form with a result of cutting work of high precisioncarried out satisfactorily.

Further, with each tip 27 supported individually by its supporting part23, fitting thereof often becomes very troublesome, particularly fittingand removal of the tips becoming more'difficult in case of. small axialpitch as the tips themselves must be reduced accordingly.

Now, according to an improved design of the present invention, so calledcompound tips 79 are provided by having a plurality of unitips 74 75 7677 corresponding to each tip supporting part 23 and also incorporatedinto a body connecting them with each other via connecting parts 78 (seeFIGS. 12-14).

In FIGS. 12-14, each of the unitips 74 75 76 77 is formed to have a flatshape of a profile of theoretical tooth form with a negative rake angleB like the tip body 36 shown in FIG. 3 5. The lower unitips 76 and 77are turned over by 180 and incorporated into the root of tooth of theupright unitips 74 and 75, so called compound tip 79 thus being formedby connecting these unitips with each other by means of the connectingparts 78 in the same pitch as the axial pitch of the tip supportingparts 23 of the cutter body 20.

In such a case, while the sides 80 81 and 82 83 of the unitips 74 75 areinclined by the lead angle +01, the sides 84 85 and 86 87 of thereversed unitips 76 77 will be inclined by the lead angle a. Thereby, itis possible to obtain the compound tip 79 capable of being reversibleupside down and inside out.

Even in case of cutting small-pitched teeth, by using said compound tips79, it becomes possible to increase working efficiency through massprocessing of the tips made easy and simplified and quick operation offitting and detaching of the tips.

Further, when fixing said compound tips 79, it is pos sible if desired,like the fixing of the tips 27 shown in FIG. 8, to fix two compound tips79 (equivalent to four times as many unitips) at a time by means of thewedges 71 formed in a large width.

From the foregoing, it will be seen clearly that the cutter according tothe present invention attains a highly economical effect throughrepeated use of the cutter body made possible by mere replacement of itstip or tips alone, and the invention also displays fully its efficiency,compensating sufficiently its cost ofconstruction even when its tips aremade from expensive materials such as cemented carbides since these tipscan be used an increased number of times due to the fact that if one ofits cutting edges is worn out or damaged, a new cutting edge will be putin service readily merely by changing the fitting posture of the verytip.

What is claimed is':

1. A rotary gear cutter having a cutting body which comprises aplurality of plain flutes arranged on its periphery parallel to its axisat fixed intervals in peripheral direction; a plurality of tipsupporting parts of hob tooth configuration arranged in the axialdirection at fixed axial intervals along but behind each said plainflute; tip locators fitted to each said plain flute and having tipsupporting holes which correspond to each each supporting part; flatshaped tips each having gear cutting edges formed in an upper body partand having a lower setting part at the root of tooth to engage with oneof said tip supporting holes; and wedges ad clamping screws for fixingsaid tips so as to be detachable freely. I

2. A rotary gear cutter as claimed in claim 1 wherein the tip body parthas two flat parallel surfaces, an upper end face normal to' said flatsurfaces and lateral sides inclined parallel with the hob tooth leadangle; the setting part arranged at the root of tooth of said tip bodybeing formed as a sub-tip of the same shape as the tip bodyv part; thetip body part and sub-tip being integrally joined but oppositelyoriented such that either the tip body part or the sub-tip may assumethe position of the other interchangeably; effective cutting edges beingformed to be supported at a negative rake angle on all the sides of eachsaid tip body and each said sub-tip,

obtaining thereby throw-away type tips capable of being freelyreversible upside down and inside out.

3. A rotary gear cutter as claimed in claim 2 wherein a plurality ofsaid throw-away tips, each comprising an integrally joined tip body partand sub-tip, are connected laterally to provide a compound throw-awaytip thereby.

4. A rotary gear cutter as claimed in claim 1 wherein of each locatorinserted in a plain flute.

1. A rotary gear cutter having a cutting body which comprises aplurality of plain flutes arranged on its periphery parallel to its axisat fixed intervals in peripheral direction; a plurality of tipsupporting parts of hob tooth configuration arranged in the axialdirection at fixed axial intervals along but behind each said plainflute; tip locators fitted to each said plain flute and having tipsupporting holes which correspond to each each supporting part; flatshaped tips each having gear cutting edges formed in an upper body partand having a lower setting part at the root of tooth to engage with oneof said tip supporting holes; and wedges ad clamping screws for fixingsaid tips so as to be detachable freely.
 2. A rotary gear cutter asclaimed in claim 1 wherein the tip body part has two flat parallelsurfaces, an upper end face normal to said flat surfaces and lateralsides inclined parallel with the hob tooth lead angle; the setting partarranged at the root of tooth of said tip body being formed as a sub-tipof the same shape as the tip body part; the tip body part and sub-tipbeing integrally joined but oppositely oriented such that either the tipbody part or the sub-tip may assume the position of the otherinterchangeably; effective cutting edges being formed to be supported ata negative rake angle on all the sides of each said tip body and eachsaid sub-tip, obtaining thereby throw-away type tips capable of beingfreely reversible upside down and inside out.
 3. A rotary gear cutter asclaimed in claim 2 wherein a plurality of said throw-away tips, eachcomprising an integrally joined tip body part and sub-tip, are connectedlaterally to provide a compound throw-away tip thereby.
 4. A rotary gearcutter as claimed in claim 1 wherein each tip locator is formed of platematerial, and has a number of tip supporting holes provided in the upperside portion thereof to engage with the lower portions of the tips atthe root of tooth of the tip supporting parts positioned behind thecorresponding plain flute into which said locator is inserted; eachlocator having tapered faces at its end portions; a locator fixingdevice for simultaneously fixing all the locators, said fixing devicecomprising a pair of clamping rings having tapers on their insideperipheries corresponding to the tapers of each locator inserted in aplain flute.